I use one of my Rimowa's to hold: travel size toothpaste, razor, shaving cream, bandages -- and then there is usually extra space in the event I need to add in anything else.

I like it because it's very solidly built and has a footprint I can consistently rely on and I know exactly where to put it in both my carry-on or my checked baggage. I've tried to use other amenity kits (e.g., the soft side Delta ones) but those soft side ones aren't quite as big and the footprint isn't consistent.

I find the soft side ones can be great for cords as mentioned by others because they don't take up a full amenity kit so by using soft-side ones, you can compress them into smaller spaces but you don't have to use a plastic bag